Simplified assessment of corroded structures

Current seismic evaluation frameworks of reinforced concrete structures such as those of ASCE/SEI 41 (2023) and EN 1998-3 (2021), are calculation-intensive and require extensive information of reinforcement ratios and detailing. However, the guidelines do not consider the condition of reinforcement, which was proven to affect the member's residual mechanical properties, the hierarchy of failure modes and the consequences on seismic performance. Considering the condition of the reinforcement complicates further the problem of seismic assessment. This paper focuses on simple modifications of existing nonlinear assessment procedures to account for the effects of moderate corrosion on seismic performance. The methodology along with an application example of computational assessment procedures of a regular five-storey structure with a soft first storey are presented, considering corrosion damage in nonlinear time history and pushover analysis. It is shown that corrosion exacerbates the seismic demands by effectively reducing the structural stiffness, while at the same time deprecating the lateral load resistance and drift capacity of the affected components. A simple criterion to determine the increased drift demand resulting from the stiffness loss due to corrosion is also included for rapid assessment procedures. • Mechanistic formulations for stiffness, strength and deformation capacity reduction due to corrosion for r.c members. • Verification of mechanistic formulations through regression attenuation coefficients from a collection of corroded columns. • Mechanistic formulations are used for rapid definition of backbone resistance envelopes, as defined by seismic codes. • Implications of member degradation on the structural scale were evaluated by analyzing to 20ground motions of 4 models of a generic structure. • An evaluation tool is proposed for rapid assessment of the implications of corrosion in increasing the seismic demands on affected structures.